: The research plan is divided into two parts, regulation at the transcriptional level and regulation at the translational level. The first part of the project is the continuation of studies to characterize the proteins that are responsible for the induction of connexin43 in the myometrium. The functional characterization of one of these proteins, a novel transcription factor, Ini, that was discovered during the previous grant period, will be completed. Three additional transcription factors that were identified by Southwestern blot and DNA mobility shift analysis will be cloned and the function of these proteins in connexin43 gene regulation studied. The likely presence of an additional estrogen-responsive transcriptional activation site in the 5'-UTR of the connexin43 gene will also be investigated. The second part of this research is based on the recent discovery in this laboratory of an internal ribosome entry site (IRES) in the 5'-UTR of the connexin43 mRNA. The function of the IRES element will be studied in bicistroni vector constructs both in vivo and in vitro. In addition, the proteins that function in the activation of the connexin43 IRES will be identified by RNA mobility shift analysis and ribosome binding assays.